1. Field of the Invention
The present invention relates to an ink-jet recording apparatus which performs recording by discharging ink on a recording medium and a control method thereof. More particularly, the invention relates to an ink-jet recording apparatus which permits recording on two surfaces of the recording medium and a control method thereof.
2. Description of the Related Art
Recording apparatuses recording images comprising dot patterns on a recording medium such as paper and a plastic sheet on the basis of recording information are generally known as applicable to printers, copying machines and facsimile machines.
Types of recording for forming an image comprising dot patterns as described above include the ink-jet type, the wire dot type, the thermal type and the laser beam type. Among these, the ink-jet type discharges and ejects ink (recording solution) drops from a discharge port of a recording head, and causes adhesion thereof to a recording medium, thereby accomplishing recording. This type can therefore provide an advantage of allowing construction at a relatively low cost. In this ink-jet type, however, which uses ink composed of an aqueous solution, in order to ensure sufficient fixing of the recorded image, it is necessary to vaporize the water content of the ink discharged onto the recording medium, thus requiring some time (fixing time).
In an apparatus of a low recording speed, since there is a time available before recording of the next page, fixing of ink has posed almost no problem. However, in a high-speed recording type ink-jet recording apparatus outputting five or more A4-size sheets per minute, particularly, in a recording apparatus outputting ten or more sheets per minute, there is a risk of an occurrence of smears during paper discharge. More specifically, in an ink-jet recording apparatus permitting high-speed recording, if there exists a region of a high recording ratio, the next recorded recording medium is discharged while ink drying is still incomplete and overlaps the latter. The insufficiently dried ink adheres to the back of the next recording medium, thus causing a feat of image deterioration on the previously discharged recording medium discharged in advance, and of an occurrence of smears in which the back of the recording media discharged next is stained.
In the ink-jet recording apparatus, a smear may also be produced when automatically performing recording on two surfaces of the recording medium. That is, in an ink-jet recording apparatus having a double-sided recording function, after performing recording on one of the surfaces of the recording medium (hereinafter referred to as the “surface” or the “first recorded surface”), the recording medium is fed again into a conveyance path for reversing. The recording medium is reversed here, and the recording operation is applied to the other surface thereof (hereinafter referred to as the “back” or the “second recorded surface”). This leads to re-introduction of the insufficiently dried recording medium into the conveyance path for reversing. The recording medium is rubbed against the conveyance path for reversing, resulting in occurrence of smears including the degrading of the recorded image, and furthermore, the thus produced smears cause another inconvenience of an occurrence of secondary smears in which the above-mentioned smears cause the ink adhering in the conveyance path to be transferred to the next recording medium.
It is therefore desirable to provide a drying period between the end of recording on one of the surfaces of the recording medium and the start of recording on the other surface (back) of the recording medium, and reverse the recording medium after ensuring sufficient drying of ink to prevent an ink stain from occurring. Under the current circumstances including an increasing demand for a higher speed and a higher quality, the drying period should preferably be the shortest possible. An apparatus for inhibiting ink stains by setting a drying period in response to the number of ink application runs to the entire area of one of the surfaces of the recording medium, without providing an excessive drying period has been proposed (for example, see the U.S. Pat. No. 6,149,327 specification).
However, in the technology disclosed in the above-mentioned U.S. Pat. No. 6,149,327 specification, in which drying time is set in response to the number of recorded dots over the entire area of one surface of the recording medium, even with a small area having a high printing duty (for example, a small solid printing area), the number of recorded dots is determined to be small as a whole, resulting in setting of a short drying period. In a state in which drying of a solid printing area has not as yet been accomplished, the recording medium is input again into the conveyance path. This leads to a possibility of an occurrence of stains caused by the ink.
When performing two-side recording with dye-based ink, dye-based ink tends to easily penetrate into the recording medium. The ink discharged onto one surface penetrates too far into the recording medium, i.e., a phenomenon known as ink fallout may occur. In this case, the content recorded on the one surface is transferred to the other side, and similarly, the content of recording discharged onto the other side is transferred to the first side, thus causing a problem in that it becomes difficult to discriminate the recorded content.